In my last post, I addressed some of the issues involved in achieving an accurate picture of one's dietary intake based on the nutrition labels on packaged foods. I touched on the discrepancies between measurement by weight and by volume, between the approximated number of servings on the label and the number of servings based on posted content weight, and discrepancies between posted net weight and both real and usable content weight.
Having left off with food that sticks to the cup or can and cannot be removed (and thereby eaten), let's continue the theme by addressing food that is not consumed because it sticks to the pot, the serving dish, the plate... or because it has not been sopped up by a bite of meat, a crust of bread, or a human tongue (i.e., licking the plate). This is perhaps of more interest to those who must "eat to their insulin" -- if the food remnants are a large enough proportion of a pre-bolused meal, the result could be a post-postprandial low. It could also become an issue if one is trying to eat enough calories to gain weight (perhaps in recovery from an eating disorder), or to consume a threshold level of a particular micronutrient, in which the dish in question is particularly rich.
Another significant source of nutrition-counting error is evaporation during cooking. My can of Progresso soup says the volume of 1 serving is 1 cup -- but after I've let the 2-cup can's contents boil for a minute or two on the stove, there may be only 1 3/4 cups left in the pot. What has evaporated is water, with the result that a cup of the remaining fluid contains just over one and one quarter servings of carbs and sodium. And as anyone who has ever doled out soup well knows, it's all but impossible to split all of the add-ins evenly across all servings. It always seems that someone gets all the mushrooms and someone else gets all the potatoes... leading to variations in carb count and glycemic load.
"Free foods"... aren't really. Some years ago, I remember reading about a woman who could not lose weight, even substituting a butter substitute that was "zero calories per squirt" for butter. It turned out that the substitute had 900 calories per container, and she was going through the better part of a container a day. If you are counting calories, every "free food" calorie must be counted along with the rest of one's foods. If you are on exchanges, every nutrient gram in a "free food" needs to be adjusted towards a partial exchange of something. If you are on insulin, consuming several servings of a "free food" at a sitting may require adjusting your bolus.
The "scaling up" issue also suggests that if we cook ahead, or cook for a family, we might be better served with labels that include both per-serving and per-package nutritional information.
Once we've accounted for all, or most, of the easily-measured, one-size-fits-all causes of variability in the food we've consumed, we have the all of the YDMV stuff: accounting for protein, fat, glycemic load, total caloric count of the meal, and how all of that affects us as individual persons with diabetes. I'll get into that particular rant tomorrow.
